PHP const Keyword Explained

With PHP we can define such variables whose values can not be changed after assigning. These varibles called CONSTANTS.

What is const?

Constants are one type of variable which we can define for any class with keyword const. Value of these variables can not be changed any how after assigning.

Class constants are diffrent than normal variables, as we do not need $ to declare the class constants. Values for the class constants can not be mathematical operation, function call, variable or property. It can have constant expression.

We can use these constants in interface also. If you are not sure what is Interface then you can refer this article for Interface in PHP.

If we are inside the class then values of the constants can be get using self keyword, but accessing the value outside the class you have to use Scope Resolution Operator ::.

If you access constant using class object and Arrow Operator ->, you will end up with Notice of Undefined Property.

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Avinash Zala currently working at a leading web development company as a Sr. PHP Web Developer. He is the founder of the Xpert Developer. He has completed B.E. in Information Technology. Born and brought up in Ahmedabad. He loves to code and coding is all about passion for him. Follow him on twitter at Avinash Zala & Xpert Developer.

Thank you sir for your tut, and I am very interested with frame for your example code. May I know what kind of plugin or script you used or maybe some tut for that…

http://voveris.eu Faifas

should be const FIRST_CONST;

http://www.xpertdeveloper.com Avinash

Why? If you think that Constant name must in CAPITAL form then its not true.

http://WebinSightsLLC.com David

The reason Faifas mentioned it is because it’s been a, many decades long, common practice for constants (and manifest constants) to be in all capital letters. I believe this was started in the original C and has carried through in all languages which use a variant of C style syntax (which PHP is one).

http://www.itoctopus.com itoctopus

It would have been nice if you displayed what will happen (the error that you will receive) if you try to assign a value to a constant after it’s already assigned.